Coaxial cable connector for circuit board

ABSTRACT

Connector apparatus for connecting a coaxial cable to a strip transmission line on an etched circuit board is described including a resilient socket member mounted on the circuit board and a plug member attached to the end of the cable. The plug includes a tubular inner eyelet crimped onto the jacket of the cable and surrounded by an outer eyelet which clamps a portion of the outer conductor of the cable between such two eyelets by an interference fit. One end of the inner conductor of the coaxial cable extends out of the eyelets and is inserted into a hole in the circuit board which may contain a separate tubular inner socket member for connection to the signal conductor of the strip line. An outer socket member in the form of a split sleeve having a plurality of legs attached to the circuit board is connected to the ground conductor of the strip line and resiliently holds the plug member inserted therein.

United States Patent [1 1 Peltola et a1.

[ 51 Apr. 22, 1975 1 1 COAXIAL CABLE CONNECTOR FOR CIRCUIT BOARD [75]lnventors: Ronald W. Peltola, Beaverton;

Richard F. Guarnero. Lake Oswego, both of Greg.

[73] Assignee: Tektronix. lnc.. Beaverton. Oreg.

[22] Filed: Mar. 19, 1973 [21] Appl No.: 342,554

Related U.S. Application Data [62] Division of Scr. No. 95.627, Dec. 7,1970 Pat. No.

[52] U.S. Cl. 339/177 R; 339/17 R [51] Int. Cl. 05k 1/02 [58] Field ofSearch 339/17, 177, 276. 217 5,

[56] References Cited UNITED STATES PATENTS 2.798.113 7/1957 Kollcr cta1. 339/177 E X 2,869.090 1/1959 .lohanson 339/177 E X 2.869.107 1/1959Engcl 339/17 R 2.941 028 6/1960 Eldcn ct a1 339/177 R X FOREIGN PATENTSOR APPLlCATlONS 1300111 1 6/1962 France 339/177 R l ()()7 ()53 10/1965United Kingdom 339/177 R 1.164.120 10/1958 France 339/17 R 911.74311/1962 United Kingdom 339/128 811.589 4/1959 United Kingdom 339/177 RPrinmry Examiner-Roy D. Frazier Assistant Eruminer-Terrell P. LewisAttorney. Agent. or Firm-Adrian .1. La Rue [57] ABSTRACT Connectorapparatus for connecting a coaxial cable to a strip transmission line onan etched circuit board is described including a resilient socket membermounted on the circuit board and a plug member attached to the end ofthe cable. The plug includes a tubular inner eyelet crimped onto thejacket of the cable and surrounded by an outer eyelet which clamps aportion of the outer conductor of the cable between such two eyelets byan interference fit. One end of the inner conductor of the coaxial cableextends out of the eyelets and is inserted into a hole in the circuitboard which may contain a separate tubular inner socket member forconnection to the signal conductor of the strip line. An outer socketmember in the form of a split sleeve having a plurality of legs attachedto the circuit board is connected to the ground conductor of the stripline and resiliently holds the plug member inserted therein.

1 Claim, 8 Drawing Figures FATENTED APR 2 2 I375 SHEET 1 0F 2PATENTEDAPRZZI-SYS sum 2 or 2 m GI COAXIAL CABLE CONNECTOR FOR CIRCUITBOARD This is a division of application Ser. No. 95,627, filed Dec. 7,I970.

BACKGROUND OF THE INVENTION I The subject matter of the presentinvention relates generally to electrical connectors for cables and. inparticular. to connectors for connection of a coaxial cable to a stripline type transmission line on an etched circuit board.

The coaxial cable connector of the present invention includes aresilient outer socket member in the form of a split sleeve having legswhich are soldered to the circuit board, and a plug member including twotubular eyelets attached to the end of the outer conductor of suchcable. The plug member is inserted into such outer socket member whichacts as a guide so that the end of the inner conductor of the cableextending out of the plug member is also inserted through a hole in thecircuit board which may contain a separate inner socket member. Thecircuit board may have a strip line type transmission line formedthereon with a uniform characteristic impedance equal to that of thecoaxial cable. and includes a signal conductor and a ground conductor,respectively connected to the inner socket member and the outer socketmember. As a result of its simplified construction. the coaxialconnector apparatus of the present invention is inexpensive tomanufacture and is provided with an extremely high frequency response aswell as a low standing wave ratio due to the fact that thecharacteristic impedance of the cable is maintained throughout theentire length of the connector which minimizes signal reflections.

The connector apparatus of the present invention is especially usefulfor connecting the signal input of a wide band cathode ray oscilloscopeto its vertical amplifier.

Previous coaxial cable connectors for connecting to etched circuitboards have employed a plug member including a pin connected to theinner conductor of the cable and a resilient outer shield connected tothe outer conductor of such cable which mate with corresponding innerand outer socket members joined together by solid dielectric material,as shown in US. patent 2,869,090 of Johanson, granted January 13, 1959,in addition to being simpler and less expensive in construction due inpart to the use of a split sleeve socket member and the use of a bareend portion of the inner conductor of such cable as the inner plugmember. the connector apparatus of the present invention also has ahigher frequency response and a lower standing wave ratio than suchprior apparatus.

It is therefore one object of the present invention to provide animproved cable connector apparatus of simple and inexpensiveconstruction.

Another object of the invention is to provide such a connector apparatusfor connecting a coaxial cable to a strip transmission line on a circuitboard in which the characteristic impedance of the cable is maintainedthrough the entire length of the connector apparatus to provide a higherfrequency response and a lower standing wave ratio.

An additional object of the invention is to provide such a connectorapparatus with a plug means which may be attached to the cable and asocket means which may be mounted on the circuit board by automaticassembly.

A further object of the present invention is to provide such a connectorapparatus with a socket member in the form of a split sleeve whichresiliently engages a rigid plug member attached to the cable and guidesthe insertion of a bare end portion of the cable into a hole in thecircuit board for easy reliable connection operation.

Still another object of the present invention is to provide suchconnector apparatus in which the socket means includes an inner socketmember mounted in the hole in a circuit board and separate from thesplit sleeve socket member for releasable connection of the cable to thecircuit board while enabling a permanent connection merely by replacingthe inner socket member with a soldered connection.

A still further object of the present invention is to provide such aconnector apparatus in which the plug means is formed by a pair oftubular eyelet members clamping the shield wires at one end of the outerconductor of such cable therebetween to form a connector of short lengthso that the cable can extend parallel to the circuit board a shortdistance therefrom for less mounting space.

An additional object of the invention is to provide an improvedelectrical connector socket in the form of a split sleeve member havinga polygonal cross section with flat sides and mounting legs extendingfrom such sides to provide good mechanical contact with a plug member ofcircuit cross section inserted into such socket.

A further object of the invention is to provide such a connector socketwith a lower inductance to ground by providing one of the leg portionswith a shorter length extending substantially perpendicular to the mainbody of the socket and by providing a slot in such main body extendinglongitudinally along its full length.

Other objects and advantages of the present invention will be apparentfrom the following detailed description of the preferred embodimentthereof and from the attached drawings of which:

FIG. 1 is a side elevation view of the connector apparatus of thepresent invention with a portion of the circuit board broken away forclarity;

FIG. 2 is a front elevation view of the connector apparatus of FIG. 1with the plug shown removed from the socket;

FIG. 3 is an exploded view of the connector apparatus of FIGS. 1 and 2',

FIG. 4 is an enlarged horizontal sectional view taken along the line 4-4in FIG. 1;

FIG. 5 is an enlarged plan view of the inner socket member taken alongthe line 5-5 of FIG. 2;

FIG. 6 is a horizontal sectional view taken along the line 66 of FIG.5',

FIG. 7 is a plan view of the circuit board taken along the line 7-7 ofFIG. 1; and

FIG. 8 is an enlarged vertical section view taken along the line 8-8 ofFIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENT The electrical connector apparatusof the present invention is shown in FIGS. 1 and 2 and includes a socket10 mounted on an etched circuit board 12 and a plug 14 attached to oneend of an electrical cable 16. The cable 16 may be a coaxial cableincluding an inner signal conductor 18 and an outer shield conductor 20separated by solid dielectric material 22 of a suitable plasticmaterial. and a protective jacket 24 of plastic material provided overthe outer conductor 20.

The outer conductor 20 may be in the form of braided wire strands woventogether along its entire length except for shield wires 26 at one endthereof which, as shown in FIGS. 3 and 8, are separated and bent backalong the cable over an inner plug member 28. The inner plug member isin the form of a tubular metal eyelet having an outer flange portion 30extending outwardly from the side of the eyelet one end thereof, sucheyelet being crimped onto the jacket 24 of the cable. An outer plugmember 32 in the form of a second tubular metal eyelet is forced overthe inner eyelet 28 to clamp the shield wires 26 between such eyelets.Thus. the inner diameter of eyelet 32 is just slightly larger than theouter diameter of eyelet 28, in order to provide the proper spacing fora good friction fit when the shield wires 26 are between such twoeyelets. The outer eyelet 32 is also provided with a flange 34 extendingradially outward at one end thereof. Flange 34 engages the flange 30 onthe inner eyelet and during assembly such flanges shear off any excesslength of shield wires 26 which may extend between them.

The plug means 14 also includes a bare end portion ofthe inner conductor18 which extends out of the eyelets 28 and 32 after some of thedielectric 22 is trimmed off in the region where the shield wires havebeen removed. This bare end of the inner conductor is inserted throughan opening in the circuit board as hereafter discussed.

The socket means includes an outer socket member 10 in the form of splitsleeve of spring metal having a slot 36 extending longitudinally throughone side of the sleeve to provide a resilient socket member. Threemounting legs 38, 40 and 42 extend from one end of the sleeve into holesthrough the circuit board and are soldered to a ground conductor strip44 on the bottom of such circuit board. An inner socket member 46 mayalso be provided to form a releasable connection with the bare end ofthe inner conductor 18. The inner socket member 46 is a tubular memberseparate from the outer socket member 10, and is mounted in an openingextending through the circuit board by soldering to metal plating 47 onthe walls of such opening as shown in FIG. 6. A signal conductor strip48 is provided on the bottom of the circuit board uniformly spaced fromthe ground conductor 44 to form a strip line type transmission linehaving a uniform characteristic impedance equal to that of the coaxialcable 16, as shown in FIG. 7. The inner socket member 46 is connected toone end of the signal conductor 48 by its soldered connection. Thus, theinner conductor 18 of the coaxial cable is connected to the signalconductor 48 of the strip line through the inner socket member 46, whilethe outer conductor 20 0f the cable is connected to the ground conductor44 of such strip line through the outer socket member 10 and plug eyelet32. It should be noted that the inner socket member 46 can be eliminatedand the bare end of the inner conductor l8 soldered in the plated hole47 to form a per manent connection to the signal conductor strip 48.Also, a ground plane 49 and an annular soldering tab 51 spaced therefrommay be provided on the top of the circuit board for shielding the stripline and to facilitate soldering of the socket members.

As shown in FIG. 4, the outer socket member 10 is of a polygonal crosssectional shape which may be an octagon including four flat sideportions 50 which engage the outer eyelet 32 of the plug at pointcontact areas since such eyelet has a circular cross section whose outerdiameter is slightly larger than the distance between two opposed flatside portions 50. The three mounting legs 38, 40, and 42 extend fromthree of the four flat sides 50 while the fourth flat side is divided bythe slot 36. As a result, it is easier to form the leg portions merelyby bending flat sheets of metal extending from the main body portion ofthe socket.

The two opposed legs 38 and 42 each extend at an acute angle ofapproximately 45 to the side of the main body portion of the socketmember 10 at a point midway down such sides as shown in FIG. 2. Legs 38and 42 are formed by providing notches 52 in the main body portion onopposite sides of such legs extending approximately half the length ofsuch body portion as shown in FIG. 1. The third leg 40 extendssubstantially perpendicular to the side of the main body portion of thesocket member 10 at a point on its bottom end so that such leg is of ashorter length than the other legs 38 and 40 in order to reduce itsinductance and provide good electrical ground for the socket member tothe ground plane 49 on the circuit board. The other two legs, 38 and 40primarily serve as the resilient mounting legs which resiliently urgethe flat side portions 50 of the socket 10 into engagement with theouter eyelet member 32 of the plug 14. The longitudinal slot 36 in thesocket member 10 not only enables it to resiliently engage the plug witha springlike action but also re duces the inductance of such socketmember.

As shown in FIG. 3, each of the legs 38, 40 and 42 are each providedwith a pair of shoulders 54 which act as stops for engagement with thesurface of the etched circuit board. The legs also each include a tabportion 56 projecting from such shoulders through the mounting hole inthe printed circuit board to enable soldering to the conductive surfaceof such printed circuit board. In addition, while not shown, such tabs56 can be made sufficiently long to enable the end of the tab portion onthe opposite side of the circuit board from the shoulder 54 to be bentover for preliminary attachment of the socket to the etched circuitboard before soldering. In any event, the socket members 10 and 46 areautomatically machine assembled on the circuit board and dip soldered.

As shown in FIGS. 3 and 4, the inner eyelet 28 of the plug is crimpedonto the jacket 24 of the coaxial cable 16 at three crimp areas 58 onthe eyelet about mid-way along its length, such crimp portionsprojecting inwardly into frictional engagement with such jacket.

As shown in FIGS. 5 and 6, the inner socket member 46 includes aconventional spring insert member 60. The spring insert 60 may be in theform of a strip of spring metal having a plurality of slits therein toprovide separate strips, alternate ones of which are bent inwardlytoward the axis of the socket member 46 and act as leaf springs.

The inner socket member 46 and the outer socket member 10 are bothflared outwardly at the top end of such socket members to enable easierinsertion of the inner conductor 18 and the outer eyelet 32 of the plug.Also, during insertion, the outer eyelet 32 of the plug engages theouter socket member first and guides the inner conductor 18 into theinner socket member 46 upon further insertion.

It will be obvious to those having ordinary skill in the art that manychanges may be made in the details of the preferred embodiment of thepresent invention without departing from the spirit of the invention.For example. two wire cables may be employed rather than coaxial cablesmerely by attaching the ground wire between the two eyelets and usingthe signal wire as inner conductor 18. Therefore. the scope of thepresent invention should only be determined by the following claims.

I claim:

1. A coaxial cable connector for terminating an end of a coaxial cablehaving an inner conductor surrounded by a sheath of insulation with anexposed section extending outwardly from the insulation and an outerconductor surrounded by a sheath of insulation with an exposed sectionof the outer conductor extending outwardly from the sheath ofinsulation. comprising:

a first ferrule means positioned on the sheath of insulation surroundingthe outer conductor and a second ferrule means telescopically positionedon said first ferrule means, both of said ferrule means electricallyconnected by capturing the exposed section of the outer conductortherebetween. whereby both of said ferrule means and the inner conductorso assembled define a plug means;

a first connector means resiliently connected only to cable.

1. A coaxial cable connector for terminating an end of a coaxial cablehaving an inner conductor surrounded by a sheath of insulation with anexposed section extending outwardly from the insulation and an outerconductor surrounded by a sheath of insulation with an exposed sectionof the outer conductor extending outwardly from the sheath ofinsulation, comprising: a fIrst ferrule means positioned on the sheathof insulation surrounding the outer conductor and a second ferrule meanstelescopically positioned on said first ferrule means, both of saidferrule means electrically connected by capturing the exposed section ofthe outer conductor therebetween, whereby both of said ferrule means andthe inner conductor so assembled define a plug means; a first connectormeans resiliently connected only to the exposed section of the innerconductor thereby terminating the inner conductor and a second connectormeans resiliently connected to the second ferrule means therebyterminating only the outer conductor, whereby both of said connectormeans are independently connected to the coaxial cable and so assembleddefine a socket means mated to said plug means to terminate the end ofthe coaxial cable.